An Active Matrix Organic Light Emitting Diode (AMOLED) display has been widely applied due to its wide angle of view, good color contrast effect, high response speed, low cost and other advantages. However threshold voltage drift may occur due to the problem of non-uniformity of a Thin Film Transistor (TFT) array substrate in a process flow.
A traditional 2T1C pixel circuit as illustrated in FIG. 1 includes a switch transistor T1, a drive transistor T2, a storage capacitor C1 and an Organic Light Emitting Diode (OLED), where a gate of the switch transistor T1 receives a scan signal Scan including signals on a gate line connected with the pixel circuit, a source (or a drain) of the switch transistor T1 receives an image data signal Data, the drain (or the source) of the switch transistor T1 is connected with a first terminal of the storage capacitor C1, a second terminal of the storage capacitor C1 receives a first drive signal VDD, a source of the drive transistor T2 receives a first drive signal VDD, a gate of the drive transistor T2 is connected with the first terminal of the storage capacitor C1, the drain of the drive transistor T2 is connected with a first terminal of the OLED, and the second terminal of the OLED receives a second drive signal VSS. When the gate of the switch transistor T1 receives a startup signal in the scan signal Scan, the switch transistor T1 is turned on, and the image data signal Data received by the source (or the drain) thereof is transmitted to the drain (or the source) of the switch transistor T1 and stored in the storage capacitor C1, and the operation of the drive transistor T2 is controlled by the image data signal Data and the first drive signal VDD so that the OLED is driven by drain current of the drive transistor T2 to emit light. In such 2T1C pixel circuit, since the drain current driving the OLED to emit light is dependent upon the threshold voltage of the drive transistor T2, the current driving the different OLEDs to emit light will be different even when the different OLEDs receive the same image data signal due to the different threshold voltage of the drive transistors T2 in the different pixel elements, thus resulting in non-uniform display of the entire image.
In summary, with the traditional organic light emitting diode pixel circuit, when the different OLEDs receive the same image data signal, the current driving the different OLEDs to emit light will be different due to the different threshold voltage of the drive transistors in the different pixel elements, thus resulting in non-uniform display of an image on the entire display panel.